The present invention relates to a mechanism for opening and closing a mercury sphygmomanometer. More particularly, the present invention pertains to a mercury sphygmomanometer opening and closing mechanism whereby a valve which is attached to a mercury passage is automatically opened and closed in response to an operation of opening and closing a cover for the apparatus.
A typical conventional mercury sphygmomanometer will be briefly described hereinunder with reference to FIG. 5.
Referring to FIG. 5, a mercury passage 1 is connected to a mercury reservoir 2 through a communicating tube 3. The tube 3 is provided with a cock 4 which is opened and closed by means of a handle 5.
A cuff, or wrapping sleeve, 6 is connected to the mercury reservoir 2 through a tube 7 and also connected to a bulb 9 through a tube 8. The mercury passage 1 is provided at its upper end with a filter 10 and a small bore 11 through which the mercury passage 1 is communicated with the outside air. The reference numeral 12 denotes mercury contained in the mercury reservoir 2.
In actual use, the cuff 6 is wrapped around the arm and, with the cock 4 opened, air is pumped into the cuff 6 by means of the bulb 9. In consequence, the mercury 12 in the mercury reservoir 2 rises through the mercury passage 1, thus enabling measurement of blood pressure.
After the use, the mercury passage 1 is tilted to return all the mercury remaining in the passage 1 to the mercury reservoir 2 and then the cock 4 is closed in order to prevent leakage and contamination of the mercury 12.
There is another type of conventional mercury sphygmomanometer having an arrangement in which a cover is formed together with the mercury passage in one unit so that, as the cover is closed, the cock is automatically closed.
Of the above-described conventional apparatuses, the former has the disadvantage that the cock must be opened and closed every time the sphygmomanometer is used and put away in the casing. The latter, that is, the prior art wherein the cock is automatically opened and closed in response to to an operation of opening and closing the cover, suffers from the disadvantage that the operational relationship between the cover and the cock is fixed such that, when the cover is open, the cock is open, whereas, when the cover is closed, the cock is closed.